What is the meaning of -um-?

related in an unspecified way. A lexical suffix with no fixed meaning or part of speech.

an agent trigger infix

intransitive verb affix

inflectional affix marking irrealis mood with transitive verbs

active verb

suffix to be used only in specific cases where the meaning is also specified

actor trigger: to do something

no trigger: expresses natural phenomena

actor trigger: to become or get

actor trigger: (with root word reduplication) to do something occasionally, at random, a little, a bit, now and then or here and there

Source: wiktionary.org

See also